Information recording cards have become used prevalently in recent years, and active R&D activities have been made to develop optical cards having a large capacity which may replace magnetic cards and IC cards. There have been proposed what they call heat mode recording materials as optical recording materials for forming the recording layer of the optical card. The recording layer of a heat mode recording material is scanned with a spot of an energy beam, such as a laser beam, to change the state of portions thereof for recording. The heat mode recording material is a metal thin film, such as a bismuth thin film, an organic thin film, such as a polystyrene thin film or a nitrocellulose thin film, or a low-valence tellurium oxide film subject to phase transition when exposed to heat. Those optical recording materials do not need any subsequent treatment, such as a developing treatment, after information has been written thereto, and information written thereto can be verified after writing. An optical card provided with such an optical recording material is a DRAW (direct read after write) medium which is capable of high-density recording, has a large capacity and allows additional writing.
In the optical card having an optical recording part of such an optical recording material, information once written to the optical recording part cannot be changed. Therefore, a new storage area is used every time data to be successively changed, such as a directory of recorded data (retrieval information) or a FAT (file allocation table), is written to the optical recording part and thereby a data storage area available for storing essential data is reduced. With such a problem in view, there has been proposed an optical card with a built-in IC module formed by mounting an IC module having an IC chip on an optical card, and capable of storing data which is to be rewritten, such as a directory or a FAT, in the IC module.
When reading data from such an optical card with a built-in IC module, a host computer needs only to specify a file name, and a card drive makes a quick electrical access to the IC chip, retrieves a directory, and records a track number indicating a track on which the specified data file is written. Subsequently, an optical pickup makes an access to the track of the optical recording part to read the specified data file. If format is standardized, the optical card with a built-in IC module can freely be used in all network systems. Although the optical recording part is not rewritable, data which needs rewriting are recorded on the IC chip because the IC chip is relatively easily rewritable.
Generally, the optical card with a built-in IC module employs an IC chip with a built-in CPU combined with an IC memory. An IC module included in such an optical card with a built-in IC module has a base, an IC chip formed on the base, and a terminal part formed on the base. The terminals of the terminal part of the IC module are brought into contact with a contact head included in a read/write (R/W) device to connect the IC module electrically to the R/W device so that I/O lines are established. Information is read and written through the I/O lines. The internal CPU of the IC chip performs advanced decisions and operations to maintain the security of the information.
The optical card with a built-in IC module having the optical recording part and the IC module is thin and its thickness is standardized (0.76.+-.0.08 mm, ISO Standards) and the optical recording part is required to be installed at a standard depth of 0.4.+-.0.05 mm from the surface of the optical card. The R/W device for writing information to and reading information from the optical recording part is constructed so as to meet those standards. The horizontal position of the optical recording part with respect to the right side, the left side and the lower side of the optical card is specified in ISO Standards (ISO 11694-2). According to ISO Standards, the distances from the right and the left edge of the optical card to the ends of a region for the optical recording part must be 3 mm or less, and the distance from the lower edge of the optical card to the end of the same region must be 4.5 mm or less. Therefore, an area taken by the optical recording part needs to be expanded toward the upper edge of the optical card to increase the capacity of the optical recording part.
Thus, the region for the optical recording part needs to be expanded to a terminal region for the terminal part of the IC module specified in ISO Standards (ISO 7816-2) for IC modules, to increase the capacity of the optical recording part of the optical card with a built-in IC module. If the region for the optical recording part is expanded, the optical recording part and the IC module overlap each other and, since the thickness of the IC module is about 0.6 mm, the thickness of a contact region of the optical card increases beyond the standard thickness of 0.76.+-.0.08 mm specified in ISO Standards, so that the IC module should not penetrate the optical recording film.